Small size particles, in particular microparticles or nanoparticles, are used in a very wide variety of technical fields, such as cosmetics, medicine, pharmacology, microelectromechanical systems (MEMS), printing, inks, inkjet inks, toners, semiconductors, sensors, catalysis, elastomers reinforcement, polymers reinforcements, coatings, plastic, rubbers, and the like. Other applications include ceramics, colorants, abrasion-resistant polymers, electrophotography, flavor enhancers, pesticides, or lubricants. They can indeed modify the chemical or mechanical properties of the medium in which they are introduced.
However, when dispersed in a medium, particles tend to aggregate because of interaction forces between each other, thereby destabilizing the dispersions. The medium of dispersion therefore has to be carefully adapted to the specific chemical properties of each particle in order to obtain stable dispersions and stability additives are often additionally required.
One approach to stabilize particles in dispersion is to adsorb or graft polymers to their surface. Repulsion occurs between the particles due to steric or electrostatic interactions induced by the polymer chains within the dispersing medium, thereby stabilizing the dispersion.
However, for steric or electrostatic interactions to occur, the polymer needs to be solubilized into the dispersing medium. Therefore, the particles grafted or adsorbed with the polymer can only be dispersed in some specific media that are able to solubilize the polymer. Thus, with this approach, once the particles are grafted with the polymer, it is not possible to disperse them in any kind of medium.
Moreover, once the particles are grafted or adsorbed with the polymer on their surface, they can no longer be recovered as bare particles and reused. Hence, the chemical modification of the particles is not reversible.